During the past few years we have studied the effect of perturbation of amine metabolism on several functions of the anterior segment of the rabbit eye, e.g., the inhibition of ciliary monoamine oxidase (MAO) by topically administered inhibitors, and the marked reduction of the formation rate of the aqueous humor by the same procedure. These and related observations form the basis of our new plans. (a) By systematically analyzing the in vivo interaction between MAO and various inhibitors we expect to make some contributions to the management of certain forms of glaucoma. (b) When to the anterior segment of the eye, we administer adrenergic drugs which are either substrates of MAO or which release monoamines from their storage sites, we are able to modify and potentiate their action. (c) By modifying the dopaminergic system of the retina, we are looking for correlations between the dopamine metabolism and the electroretinogram. (d) In order to provide a better basis for these and many other studies, we have initiated the analysis of the course of inhibition of purified MAO by stopped-flow measurements, and the characterization of ocular MAO with respect to A and B types.